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  <div class="section" id="module-imghdr">
<span id="imghdr-determine-the-type-of-an-image"></span><h1><a class="reference internal" href="#module-imghdr" title="imghdr: Determine the type of image contained in a file or byte stream."><code class="xref py py-mod docutils literal notranslate"><span class="pre">imghdr</span></code></a> --- 推测图像类型<a class="headerlink" href="#module-imghdr" title="永久链接至标题">¶</a></h1>
<p><strong>源代码</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.7/Lib/imghdr.py">Lib/imghdr.py</a></p>
<hr class="docutils" />
<p><a class="reference internal" href="#module-imghdr" title="imghdr: Determine the type of image contained in a file or byte stream."><code class="xref py py-mod docutils literal notranslate"><span class="pre">imghdr</span></code></a> 模块推测文件或字节流中的图像的类型。</p>
<p><a class="reference internal" href="#module-imghdr" title="imghdr: Determine the type of image contained in a file or byte stream."><code class="xref py py-mod docutils literal notranslate"><span class="pre">imghdr</span></code></a> 模块定义了以下类型：</p>
<dl class="function">
<dt id="imghdr.what">
<code class="descclassname">imghdr.</code><code class="descname">what</code><span class="sig-paren">(</span><em>filename</em>, <em>h=None</em><span class="sig-paren">)</span><a class="headerlink" href="#imghdr.what" title="永久链接至目标">¶</a></dt>
<dd><p>测试包含在命名为 <em>filename</em> 的文件中的图像数据，并且返回描述此类图片的字符串。如果可选的 <em>h</em> 被提供， <em>filename</em> 将被忽略并且 <em>h</em> 包含将被测试的二进制流。</p>
<div class="versionchanged">
<p><span class="versionmodified">在 3.6 版更改: </span>接受一个 <a class="reference internal" href="../glossary.html#term-path-like-object"><span class="xref std std-term">类路径对象</span></a>。</p>
</div>
</dd></dl>

<p>接下来的图像类型是可识别的，返回值来自 <a class="reference internal" href="#imghdr.what" title="imghdr.what"><code class="xref py py-func docutils literal notranslate"><span class="pre">what()</span></code></a>：</p>
<table border="1" class="docutils">
<colgroup>
<col width="26%" />
<col width="74%" />
</colgroup>
<thead valign="bottom">
<tr class="row-odd"><th class="head">值</th>
<th class="head">图像格式</th>
</tr>
</thead>
<tbody valign="top">
<tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'rgb'</span></code></td>
<td>SGI 图像库文件</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'gif'</span></code></td>
<td>GIF 87a 和 89a 文件</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'pbm'</span></code></td>
<td>便携式位图文件</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'pgm'</span></code></td>
<td>便携式灰度图文件</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'ppm'</span></code></td>
<td>便携式像素表文件</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'tiff'</span></code></td>
<td>TIFF 文件</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'rast'</span></code></td>
<td>Sun 光栅文件</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'xbm'</span></code></td>
<td>X 位图文件</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'jpeg'</span></code></td>
<td>JFIF 或 Exif 格式的 JPEG 数据</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'bmp'</span></code></td>
<td>BMP 文件</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'png'</span></code></td>
<td>便携式网络图像</td>
</tr>
<tr class="row-odd"><td><code class="docutils literal notranslate"><span class="pre">'webp'</span></code></td>
<td>WebP 文件</td>
</tr>
<tr class="row-even"><td><code class="docutils literal notranslate"><span class="pre">'exr'</span></code></td>
<td>OpenEXR 文件</td>
</tr>
</tbody>
</table>
<div class="versionadded">
<p><span class="versionmodified">3.5 新版功能: </span><em>exr</em> 和 <em>webp</em> 格式被添加。</p>
</div>
<p>你可以扩展此 <a class="reference internal" href="#module-imghdr" title="imghdr: Determine the type of image contained in a file or byte stream."><code class="xref py py-mod docutils literal notranslate"><span class="pre">imghdr</span></code></a> 可以被追加的这个变量识别的文件格式的列表：</p>
<dl class="data">
<dt id="imghdr.tests">
<code class="descclassname">imghdr.</code><code class="descname">tests</code><a class="headerlink" href="#imghdr.tests" title="永久链接至目标">¶</a></dt>
<dd><p>执行单个测试的函数列表。每个函数都有两个参数：字节流和类似开放文件的对象。当 <a class="reference internal" href="#imghdr.what" title="imghdr.what"><code class="xref py py-func docutils literal notranslate"><span class="pre">what()</span></code></a> 用字节流调用时，类文件对象将是 <code class="docutils literal notranslate"><span class="pre">None</span></code>。</p>
<p>如果测试陈工，这个测试函数应当返回一个描述图像类型的字符串，否则返回 <code class="docutils literal notranslate"><span class="pre">None</span></code>。</p>
</dd></dl>

<p>示例:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">imghdr</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">imghdr</span><span class="o">.</span><span class="n">what</span><span class="p">(</span><span class="s1">&#39;bass.gif&#39;</span><span class="p">)</span>
<span class="go">&#39;gif&#39;</span>
</pre></div>
</div>
</div>


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